They were trying to take back land they lost in WWI.
After the attack on Pearl Harbor, Japanese Americans were subjected to harsh treatment back in the US Mainland. Internment camps were set up on the orders of FDR. Japanese Americans were forced into these camps regardless of citizenship which brought up the constitutionality of order 9066. The Supreme Court case Korematsu v. US started when Fred Korematsu decided not to leave his home and decided not to comply with the order, he was then arrested. During the case the Supreme court ruled that this was a “military necessity” and not a racial matter.
Meanwhile in Germany, Hitler and fascist Germany decided to create a perfect aryan race and try and become the leader of the world. He persecuted what he thought to be the inferior religions, such as gypsies and the jewish, and killed many other Europeans to “further refine” his